This invention pertains to high pressure insulating flanges for pipelines. More particular, it relates to a specially constructed nonyielding strong electrical isolation gasket for flanges that use metallic seal rings.
In the pipeline industry, insulating couplings or flanges are used for many purposes. For example, the design, construction, operation, maintenance and salvage of metal pipelines, including flowlines and well casing, depend in part on the control of external corrosion of such tubular goods. External corrosion is caused when a pipeline is made up of metal tubular goods having different surface potentials either due to dissimilarity in metal composition or in surface newness or preparation, or when electrically connected corrosive metal tubular goods traverse different electrolytic environments, or when the electrically connected metal tubular goods pick up stray or induced electrical currents which are later discharged into the soil or water around the tubular goods. A similar form of corrosion occurs inside the pipe if the fluid in the pipe is an electrolyte. These types of external corrosion are typically controlled by disrupting the electrical circuits with electrical isolating flanges and by cathodic protection, or protective coatings or wrappings, or both. Many types of electrical isolating flanges have been proposed; but most are unsuitable for use with API and ANSI ring-joint or seal ring flanges and are unreliable for pressures at or above 2500 p.s.i.g.
It would, therefore, be desirable to provide a more reliable high pressure electrical isolating API or ANSI ring-joint flange, especially one that is useful between dissimilar metals.